1. Field of the Invention
The present invention relates an antenna apparatus, and especially relates for an antenna apparatus having the vertically and horizontally omni-directional radiation pattern so as to improve the quality of the transmitted signal of the antenna.
2. Description of the Related Art
A local area network (LAN) means that several computers are connected each other in a specified area. For instance, two or more computers have working stations installed thereon and are connected through cable or wireless communication. Therefore, computers in the LAN can share and transmit data.
Most computers recently are connected through cables. However, the following defects will be occurred because of using cables to form the LAN. Firstly, it is difficult and expensive to change the location of the client computer after completely installation of the network. Second of all, the cable should be added or removed if new client computer have been changed. This would be heavy work for the network provider. Thirdly, a cable network installation may have a great influence on the view of the building. Furthermore, the cable network installation is not so flexible in arrangement.
For stated above, wireless LAN technology is increasingly developed and it is intend to replace the cable network installation. There is many communication manufactories, i.e. IBM, Ericsson, Mobile Communications, Nokia, Toshiba and Intel Corp., develops a Bluetooth protocol for the wireless communication within a short distance about 150 meters.
Please refer to FIG. 1, which shows a circuit diagram of a wireless network device. The circuit diagram comprises an antenna apparatus 10, a RF unit 12 and a DSP unit 14 wherein the RF unit 12 has a low noise amplifier (LNA) 121, a power amplifier (PA) 123 and a mixer 125. The antenna apparatus 10 is used for receiving and transmitting signal. When the antenna apparatus 10 receiving the signal, it is processed with the filter by the power amplifier 123 and the descending frequency by the mixer 125 such that the DSP unit 14 can be used for decoding radio frequency signal. On the other hand, when the signal is transmitted through the antenna apparatus 10, it is coding by the DSP unit 14 and the signal is processed with the filter by the power amplifier 123 and the rising frequency by the mixer 125.
When transmitting the signal, the important component is the antenna and the quality of the communication, the range of the communicating and the transmitting rate are dependent on the performance of the antenna. As the allocation of the client computer is flexible, especially for the portable computer users, it is hard to predict the using condition of the client computer. Therefore, the requirement of the antenna is to receive or transmit the signal without the direction limit. That is, an omni-directional radiation pattern of antenna is required for using in the wireless communication.
Referring to FIG. 2, a conventional wireless device such as a rod antenna 22 is shown. The position of the rod antenna 22 should be perpendicular to one horizontal surface if a horizontally omni-directional radiation pattern is required. However, such installation will cause a bad vertical radiation pattern performance. On the other hand, the position of the rod antenna 22 should be perpendicular parallel to one horizontal surface if a vertical omni-directional radiation pattern is required. However, such installation will cause a bad horizontal radiation pattern performance. For stated above, it is hard to find an installation of the rod antenna 22 that the vertically and horizontally omni-directional radiation pattern be achieved.
The conventional wireless apparatus for using the rod antenna comprises the following shortcomings. The rod antenna is installed for external application and the performance of the rod antenna depends of the length and the height thereof. However, the increasing size of the rod antenna causes inconvenience to users and such product may not be competitive with other similar product. Finally, the external antenna usually is made by manufacturers rather than the system manufacture such that the total cost of the system will be increased.
Therefore, it is necessary to develop a low cost and small size antenna with high transmitting performance for wireless network manufacturers. Furthermore, an antenna apparatus having the vertically and horizontally omni-directional radiation pattern is developed by the applicant and it can be received within the computer system.
Therefore, it is an objective of the present invention to provide an antenna apparatus for providing the vertically and horizontally omni-directional radiation pattern.
Another object of the present invention is to provide an antenna apparatus with a simple structure so as to lower the cost of the antenna and to easily be made.
Another object of the present invention is to provide a small volume of an antenna apparatus so as to be received within the wireless card.
The antenna apparatus of this invention is utilized in the wireless communication and comprises a first antenna plate, a second antenna plate and a matched circuit. The matched circuit has a front line and a transferring line so as to be formed as an appropriate impedance between the first antenna plate and the second antenna plate, wherein one end of the transferring line is coupled to the front line forming a T shaped converging portion having a first feedback point and a second feedback point. The first antenna plate has an electrical foot connecting to the first feedback point and a ground foot connecting to the ground. Similarly, the second antenna plate has an electrical foot connecting to the second feedback point and a ground foot connecting to the ground.
The first antenna plate and the second antenna plate are L shaped metal plates and are arranged symmetrically to form the like of an annulus rectangular so that a horizontally omni-directional radiation pattern can be accomplished. Furthermore, the antenna plates and the feet thereof form an inversed F shape and a specific height of the antenna apparatus can be maintained so that a vertically omni-directional radiation pattern can be accomplished. Therefore, the antenna apparatus of the present invention can provide the vertically and horizontally omni-directional radiation pattern so as to improve the quality of the transmitted signal of the antenna.